Technical or industrial scale installations are found in the most diverse areas of industry, being used for example to manufacture a specific product, to further process or refine raw materials, to carry out previously manual activities in an automated manner or to produce in particular electrical energy. Finished industrial scale installations, such as power plant installations in particular, generally consist of a plurality of installation components, which realize the individual functions of the respective industrial scale installation. Many such installation components are subject to mechanical or operationally induced wear during their operating life. During the service life of the technical installation wear of the installation components represents an important aspect even as early as the design stage of the installation, as if a wear limit is exceeded, the function of the technical installation or at least of the affected components can no longer be insured.
In power plant installations in particular parts or installation components such as boilers, steam generators, collectors, conduits and the like are subjected to changing mechanical stresses due to changes in the parameters of their environments such as pressure and temperature for example. These different loadings, or load changes of the power plant installation, which are generally associated with a change of state of the power plant installation, for example an increase in or reduction of output, normally result in possibly considerable material strain in the affected component and to so-called part fatigue, which above a certain limit can also result in part failure. In particular such fatigue limits the operational life or maximum permissible operating life of the respective power plant component or installation component. For these reasons part fatigue of selected installation components is taken into account during the planning of an industrial scale installation and also during the planning of repair and maintenance cycles, in order to be able to insure replacement of the respective components as required in good time before part failure.
To take appropriate account of such fatigue phenomena during installation planning, during the construction or design of power plant parts, to insure a minimum service life, the respective components or parts are generally subjected to a predefined load spectrum consisting of a limited number of types of load change, for example comprising a predetermined number of hot starts, warm starts and cold starts each with predefined modes of operation of the power plant installation.
For these standardized types of load change the respective fatigue contributions in the affected components are then determined for each type of load change, with relatively complex computation methods, such as finite element calculations, generally being deployed. The respective installation components are then generally designed taking into account the results thus obtained such that the overall fatigue of the respective part or component determined for each type from the individual fatigue contributions and the number of load changes applied does not exceed a predetermined limit value for fatigue deemed still to be permissible.